<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
   请输入城市: <input type="text" id="city">
</body>
</html>
<script src="jquery-3.3.1.min.js"></script>
<script>
    $("#city").blur(function () {
        var city=$(this).val();
        $.ajax({
            url:"qi.php",
            data:{city:city},
            dataType:"json",
            type:"post",
            success:function (res) {
                console.log(res);
            }
        })
    })
</script>